The present invention relates to a laser optical device to align a laser beam to an incident surface of an optical fiber and an operating method of an actuator.
The laser optical device is to emit light by a semiconductor laser element (hereinafter called LD), propagates a laser signal light modulated by information to an optical fiber or propagates a laser signal light emitted from a optical fiber to the other optical fiber and is configured with optical parts such as LD, a condenser lens to condense the laser signal light form LD or the optical fiber and the optical fiber.
In such laser optical device, LD and the condenser lens have to be aligned with high accuracy in respect to the optical fiber having a core diameter of some μm, thus generally these optical parts are firmly fixed by welding or by an adhesive.
However, even if the laser optical device is configured by adhesive so that the relative position of the parts is accurately aligned and firmly fixed is such way, the following problems remain. First, in case the laser optical device is manufactured in the above way, the quality of the product can be checked only after adhesion and drying. Also, it is considered that achieving of a high yield rate in manufacturing of such laser optical device is relatively difficult. Second, in case the performance is deteriorated with time, correction is impossible. Third, the fixed position is changed with variation in temperature. In case a laser light source is located particularly near the optical parts, an effect caused by heat generated by the laser light source is large.
Therefore, various structures of the laser optical devices to maintain high performance without being affected by environmental variation including a change of mechanical conditions such as a vibration, a change of ambience temperature and a deterioration with time have been desired and studied.
For example, there is known a technology of optical communication device (Patent Document 1) which controls to direct laser signal light to a core center, having a condenser lens to condense a laser signal light from laser light source towards an optical fiber, an actuator to move the condenser lens, a light detecting device to detect an intensity of the laser signal light conducted in the optical fiber, a polarization device to polarize the laser signal light, and a control device to control the polarization device by negative feedback with an output of the light detecting device, wherein the control device detects a change of the intensity of the laser signal light through the light detecting device while the light polarization device causes wobbling to the laser signal light in a predetermined amplitude and frequency in X-direction or Y-direction, and captures a deviation of the laser signal light from a core center of an incident surface of the optical fiber based on the detection result.    [Patent Document 1] Unexamined Japanese Patent Application Publication No. 2003-338795
Meanwhile, in order to control the laser light so as to be directed to a center of the incident surface of the optical fiber, an actuator having a micron order resolution capable of high accuracy positioning control is required. Also, the laser signal light modulated by information such as communication data and image data is required to propagate the information accurately without being affected by change of the intensity of the laser signal light caused by wobbling.
However, the optical communication device disclosed in Patent Document 1 does not have suggestion to cope with accurate propagation of the information without being affected by the change of the intensity, considering the change of the intensity of the laser signal light caused by wobbling. The optical communication device disclosed in the Patent Document 1 does not have such actuator as above having high resolution capable of highly accurate positioning control and it is thought that sub-micron order positioning controls is difficult to be implemented. Also, the condenser lens is moved through the actuator driven by a sine wave signal, and the change of the intensity of the laser light is detected while the condenser lens is moving, namely during wobbling. Therefore, a S/N rate is deteriorated and detection of change of the intensity of the laser light is difficult.